by Sean Harrison:
Questions regarding decompression sickness (DCS) are very commonly asked by divers at all levels, and answers to these questions vary depending on the experience of the diver and the level of training they have received. For a sport diver who does not plan on conducting a decompression dive, the answer can be as simple as: staying well within the no decompression limits (NDLs), controlling your ascent, and performing at least a 3 minute safety stop on every dive. For technical divers, planning decompression dives, the answers get a little more complicated but the basic theory remains the same.
A technical diver planning to perform a decompression dive has to build in more contingencies such as: additional gas supplies, multiple controlled ascent rates, variations of an optimum dive plan, and additional decompression stops, all leading to the same end result – reduced amounts of residual nitrogen in the body, off-gassed at a controlled rate. For planned decompression dives this all has to happen prior to reaching the surface.
Ideally, the nitrogen and other inert gasses that have been absorbed into our body’s tissues will return to our bloodstream and eventually be eliminated out through our lungs. However, if we do not follow our no decompression limits (NDLs) or our decompression schedules, or if we ascend too quickly, the absorbed gasses in our body will expand and form bubbles in our tissues and bloodstream. The end result being decompression sickness, also known as the bends, or “getting bent.”
What are the symptoms of DCS?
- Joint and muscle pain – this is the most common symptom due to bubbles typically forming in and around joints
- Confusion and unusual behavior
- Coughing up blood
- Difficulty urinating
- Dizziness or vertigo
- Loss of hearing or ringing in ears
- Memory loss
- Sensitive, painful, or itchy skin
- Shortness of breath
- Tingling, numbness, and paralysis
- Uncontrollable shaking
- Visual disturbances
Treatment of DCS
In most cases, DCS will require treatment in a hyperbaric or recompression facility. This helps to increase the ambient pressure surrounding the diver, shrinking the inert gas bubbles and reversing the DCS effects. The pressure is then gradually reduced to normal atmospheric pressure. The more severe the case of DCS, the more aggressive the ‘table’ is that’s used to treat it. In some cases the same table is used multiple times over multiple days. In some hyperbaric facilities a second inert gas (helium) is used in place of ambient air, this has shown to decrease the time spent in the recompression chamber and speed up the treatment. Immediate steps of treatment in the field include:
- Maintain blood pressure and administer 100 percent oxygen (if 100 percent is not available, administer the highest percentage available) and fluids
- Contact your local emergency medical services (EMS)
Prevention of DCS
- Slow and controlled ascents
- Never exceed your NDL or your planned decompression schedule
- Do not drink alcohol before diving, and stay hydrated
- Avoid flying or driving to higher elevations within 24 hours after a dive
The symptoms of DCS can appear as late as 48 hours after returning to the surface, but in most cases and certainly in extreme cases, the onset of symptoms occur immediately after surfacing, if not before. There are different categories and levels of DCS, based on the severity of the above symptoms. Some cases can be very dangerous and life threatening, so if you suspect that yourself or another diver may be suffering from DCS you need to immediately: abort the dive, administer pure oxygen ASAP, and contact your local emergency medical services (EMS). Proper dive planning, staying within your NDLs, staying within your planned decompression schedule, controlling your ascent, and properly executing safety stops can greatly reduce your risk of DCS.
There are more complex physiological considerations when it comes to DCS and its symptoms, but this should provide a basic understanding, and checklist of symptoms to be on the lookout for when diving. Make a mental note, and dive safely!
Want more info on DCS? Check out some of our past articles.
Bret Gilliam » Better Bent than Dead
Bret Gilliam » How Deep is too Deep
Dan Downes » Nobody Goes to a Hyperbaric Chamber by Choice, Right? Wrong!